The crossover between lasing and polariton condensation in optical microcavities

TL;DR

This paper investigates how different types of dephasing affect the transition from polariton condensation to lasing in microcavities, revealing a close analogy to superconductors and identifying critical dephasing thresholds.

Contribution

It introduces a model distinguishing pair-breaking and non-pair-breaking dephasing, analyzing their impact on polariton condensates and laser regimes in microcavities.

Findings

Pair-breaking dephasing reduces the condensate gap to zero at a critical point.

Weak non-pair-breaking processes cause broadening but do not destroy the condensate.

The laser regime emerges as a gapless superconductor analog at high pair-breaking dephasing.

Abstract

We study a model of a photon mode dipole-coupled to a medium of two-level oscillators in a microcavity in the presence of dephasing processes introduced by coupling to external baths. Decoherence processes can be classified as pair-breaking or non-pair-breaking in analogy with magnetic or non-magnetic impurities in superconductors. In the absence of dephasing, the ground state of the model is a polariton condensate with a gap in the excitation spectrum. Increase of the pair-breaking parameter $\gamma$ reduces the gap, which becomes zero at a critical value $\gamma_{C1}$; for large $\gamma$, the conventional laser regime is obtained in a way that demonstrates its close analogy to a gapless superconductor. In contrast, weak non-pair-breaking processes have no qualitative effect on the condensate or the existence of a gap, although they lead to inhomogeneous broadening of the excitations.